The 27-year-old 'Part Of Me' singer apparently keeps 20 Brand New toothbrushes close at hand because she is so scared of getting fillings.

A source close to Katy told the Daily Star newspaper: ''We won't go anywhere without a stack of brushes.

''When she was a kid she had 13 cavities. So she now brushes her teeth six times a day.''

Katy - who split with Russell Brand after just 14-months of marriage in December - previously revealed her tooth-cleaning obsession was inspired by Britney Spears.

In an interview with YouTube, she confessed: ''I brush my teeth all the time. I wanted them to be, like, Britney Spears white. I used to grow up seeing her music videos and be like, 'What does she do? Does she get a new set of teeth all the time? They're so white'.

''I'm really anal about that because I like good breath. A turn off for me with guys is, like, halitosis ... I'm the kind of friend that's like, 'Stick a piece of gum in your mouth, because I'm going to save some friendships for you'.

''I'll brush my teeth (after) breakfast, lunch and dinner ... I did have 13 cavities at one time, so you can imagine why I'm so freaked out. When I was a kid I didn't really go to the dentist a lot ... and when I finally went, they were like, 'You might as well get a new set of teeth'.''